This invention relates to a method of and apparatus for use in recovering oil from solid hydrocarbonaceous material. The invention has particular application in the recovery of shale oil from oil shale, and the invention is hereinafter described in such context, but it will be understood that the invention also has applications in the recovery of oil from other solid hydrocarbonaceous materials such as coal and tar sands.
In general terms, the invention flows from a realisation of the inventor that feedstock in the form of fresh oil shale particles may be contacted with hot recirculated heat medium shale in a reaction bed to form a self-sustaining dense phase fluidized bed. By contacting the fresh feed shale and the hot recirculating heat medium shale, the kerogen content of the feed shale particles is converted into gas and oil vapour products which are released at all levels throughout the reaction bed, whereby a fluidized bed is created without there being a need to introduce an appreciable amount of an external fluid, such as gas or steam, to sustain the fluidized bed.
Fluidized bed processing is used extensively in arts which may be considered vaguely related to the present invention. Thus, the Winkler coal gasification process employs a fluidized bed in which crushed coal is reacted with oxygen and steam to produce a fuel gas which is rich in carbon monoxide and hydrogen. Also, in fluid catalytic cracking plants fluidization is effected in reaction vessels by oil vapours and in catalyst regeneration vessels by combustion supporting air which is admitted for carbon burning. Furthermore, a number of prior art paper proposals have discussed the use of fluidized bed retorting for recovery of shale oil.
However, in all of the operational fluidized bed retorting processes of which the inventor is aware, fluidization of the beds is effected and sustained by the admission of substantial amounts of an external fluid. This is to be contrasted with the present invention in which fluidization is effected and sustained by a reaction of dry solids, with the fluidizing medium being constituted by gas and vapour products released in the reaction and without there being a need to admit significant amounts of external fluids other than under start-up conditions.
It is a disadvantage of fluidized bed processes using an external fluid to fluidize the bed, that the external fluid must be separated from the effluent vapour given off from the bed before the effluent varpour may be refined into end product. It also requires a supply of energy to provide and sustain the external fluid and to introduce that fluid under pressure into the fluidized bed.